$ { {5} \times \left[\begin{array}{rr}{4} & {0} \\ {2} & {0}\end{array}\right] = {?} } $
Explanation: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{5}\times{4} & {5}\times{0} \\ {5}\times{2} & {5}\times{0}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{20} & {0} \\ {10} & {0}\end{array}\right]}$